As other people said, it would be nice to finally get ANY monkey, but South America needs them way more. If we're really down to the last pack or two, I would not view the GSNM as a good pick.
Though I don't see the GSNM as a priority specifically for primate representation, it is a great animal to make the Chinese players happy. A lot of people say that North America and Europe (though there are still some open niches and a missing bear) are somewhat overrepresented, which to me is expected and totally fine. A huge chunk of the playerbase and the online community comes from those places. A lot of us want the basics for our local animals. However, Chinese players make up a big chunk of the playerbase, but the language barrier keeps many from participating in this community. East Asia isn't badly represented, but I don't think it's quite gotten the same treatment relative to its biodiversity.
From what I understand, the Golden Snub Nosed Monkey is the top missing local star animal for building Chinese Zoos. If I were trying to build a Chinese Zoo, I would also want a deer and the alligator. Already, the community wants a muntjac and some ornamental birds, especially the Mandarin Duck and Golden Pheasant. The yellow-throated marten is also a pretty cool animal. For Japanese sections, I'd also want a raccoon dog and an ungulate, probably the serow. If we're looking at another few years of DLCs, I'd hope they all get in.